Wednesday, 13 April 2011 13:26

Don’t cull cows, extend lactation

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EXTENDED LACTATION is a viable option to culling cows that do not get in calf as planned, according to new research.

This shows extended lactation can be commercially viable for pasture-based dairying systems.  The project – conducted by the Victorian Department of Primary Industries – combined trials conducted at the Ellinbank Dairy Research Institute in Victoria with dairy farmer experience through case studies.

Dairy Australia’s InCalf program leader, Dr Barry Zimmermann, says extended lactation can work well in herds with year round, split or batch calving systems.

He says the interval between calvings can be successfully extended with most Holstein cows beyond the traditional 12 months – to about 18 months. In year round, split or batch calving herds, this gives the flexibility to join an empty cow to calve with the next group, he says.

“During the extended lactation phase, you can expect their daily milk production to be less than their herd-mates on a traditional lactation, but this is compensated for by extra days in milk and higher concentration of protein.”

Zimmerman says most will continue to produce milk through to the planned dry off date.

“It is a bit trickier in a strictly seasonal calving herd, because the interval between calvings will stretch to two years. In that situation milk production tends to drop off in the last few months.

He adds that annual milk production of extended lactation cows will drop by about 2% in the top 50% of cows, but by up to 14% in the bottom half.

“Many cows won’t make the distance, drying themselves off before their planned dry off date.”

Zimmermann says it is rare to find a whole herd on an extended lactation, but it is common to find a small number of cows within a herd with an extended lactation.

He says extended lactation is a management tool used in certain situations and often on specific cows.

“For example, you can shorten the joining period and bump not-in-calf cows into the next mating group and milk them for an extended lactation. Some farmers do this to avoid using bulls, allowing all cows to be joined by AI.”

Zimmermann says with record high prices for export heifers there’s even more incentive to get more AI calves on the ground.

Farmers considering extended lactation should:

Think about the impact it will have on the herd’s milk production pattern and if there are implications for the contract with their milk processor.

Have the herd pregnancy tested so you know which cows are not in calf. You can then decide which ones you want to keep on an extended lactation and whether some will be culled.

Make sure cows are given the best opportunity to get in calf when they are joined. Follow the InCalf recommendations for heat detection and AI practices. Only allow a cow two mating periods to get in calf. Cull repeat non-breeders.

Zimmermann says farmers will need to monitor body condition and adjust nutrition if needed when cows are in the extended lactation phase.

“Special nutrition strategies are not required for cows on an extended lactation but cows on an extended lactation are very responsive to supplementary feeding and you need to beware of over-conditioning towards the end of lactation,” he adds.

“Over-conditioned cows may need to be fed as a separate group during the dry period to ensure they do not calve in body condition score of more than 5.5 (on an 8-point scale).”

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